A radiation imaging system (or “a radiography system”) may be used in many fields such as medical diagnosis and therapy, industrial production and application, scientific experiment and research, national security, etc. Generally, radiation imaging is a technology that may allow non-invasive observation of the interior of a subject using radiation. As used herein, radiation may include a particle ray (for example, neutron, proton, electron, μ-meson, heavy ion, etc.), a photon ray (for example, X-ray, γ-ray, α-ray, β-ray, ultraviolet, laser, etc.), or the like, or any combination thereof. The information acquired by a radiation imaging system may include, e.g., structure, density, or lesions, etc., without damaging the subject. The term “subject” used herein may include a substance, a tissue, an organ, an object, a specimen, a body, or the like, or any combination thereof. Exemplary radiation imaging systems in the medical field may include an X-ray imaging system, for example, a Computerized Tomography (CT) system, a Digital Radiography (DR) system, or some multi-mode imaging system incorporating with a CT or DR system. Images with certain contrast may be generated by X-ray imaging based on the difference in absorptivity, reflectivity and transmissivity of different parts in the subject. The radiation passing through the subject in a straight line (termed as “primary radiation”) may contribute to the generation of an image. Scatter radiation caused by the interaction between the radiation and the subject may interfere with the primary radiation. The scatter radiation may influence, for example, contrast-to-noise ratio (CNR) of a generated image. Thus, it is an enormous challenge to suppress or reduce the scatter radiation effectively and inexpensively in a radiation imaging system.